Mantis 1090

Add `undefineall

In P1800/D3a:

Section 21.5.2 `undef

In 21.5.2

CHANGE

The directive `undef shall undefine a previously defined text macro. An attempt to undefine a text macro that was not previously defined using a `define compiler directive can result in a warning. The syntax for `undef compiler directive is given in Syntax 21-4.

TO

The directive `undef shall undefine a previously defined text macro the specified text macro if previously defined by a `define compiler directive within the compilation unit. An attempt to undefine a text macro that was not previously defined using a `define compiler directive can result in a warning. The syntax for the `undef compiler directive is given in Syntax 21-4.

ADD

21.5.3 `undefineall

The `undefineall directive shall undefine all text macros previously defined by `define compiler directives within the compilation unit. This directive takes no arguments and may appear anywhere.